The present invention relates to a cooler box for storing food or the like, and more particularly to a cooler box that cools its interior by the use of a Stirling-cycle refrigerator.
Conventionally, various types of cooler box exist that use an electronic refrigerating device. One common type is cooler boxes that cool their interior by exploiting the properties of a Peltier device, as disclosed in Japanese Patent Application Laid-Open No. H6-307752. FIG. 27 shows an example of this type of cooler box. This cooler box is provided with a box member 301 and a cooling device 302. The box member 301 has substantially the shape of a rectangular parallelepiped, has a cooling chamber 301a formed inside it for storing food, drink and the like, and insulates heat. The cooling device 302 cools the interior of the cooling chamber 301a. 
The box member 301 is composed of a body member 303, which has the shape of a bottomed cylinder and has the cooling chamber 301a formed inside it, and a lid member 304, which is fitted on the top face of the body member 303 so as to open and close the cooling chamber 301a. The body member 303 has a body casing 305, an inner vessel 308, which is composed of an inner casing 306 and a cooling wall 307 made of a metal such as aluminum, and a heat insulator 309, which fills the space between the body casing 305 and the inner vessel 308. The interior of the lid member 304 is filled with a heat insulator 310.
The cooling device 302 has a Peltier device 311, a spacer 312, and a heat-rejecting fin 313, and is composed of a cooling unit 314, which is fixed to the inner vessel 308 with screws or the like, a cooling fan 315, and a side cover 316 for covering the cooling unit 314 and the cooling fan 315. Incidentally, this cooler box can be used also as a warmer box when the direction of the electric current supplied to the Peltier device 311 is reversed so that the interior is heated.
The conventional cooler box described above typically consumes around 48 W of electric power. Thus, when mounted on a car, the cooler box can be operated from the car""s battery without any problem. However, quite inconveniently, when used outdoors, the cooler box requires a high-capacity portable power supply for outdoor use. For example, when operated from a 12 V power supply, the cooler box, which consumes around 48 W of electric power, requires a current of 4 A. Accordingly, to use the cooler box for 10 hours or more, it is necessary to use a portable power supply with a capacity of 40 Ah or higher.
It is difficult, however, for a general user to obtain a portable power supply with such a high capacity, and, even if one is available, it is extremely expensive. Therefore, the user has no choice but to depend on electric power commercially distributed to a household or on a battery of a car. It is to be noted that the units used above are as follows: W stands for watts, V stands for volts, A stands for amperes, and h stands for hours.
In the conventional cooler box described above, a Peltier device is used as the cooling device. However, the lowest temperature produced by a Peltier device is about 0xc2x0 C., and therefore it does not offer cooling performance comparable with that of a freezer (with an interior temperature of about xe2x88x9218xc2x0 C.). Moreover, in the conventional cooler box, the volume of the cooling chamber cannot be varied. This often leads to inefficient cooling, with the cooling performance of the cooler box used wastefully to cool an article that can be cooled with lower cooling performance. Furthermore, in the cooler box described above, the Peltier device cools part of the wall surface of the box member. Thus, the interior temperature tends to vary from place to place.
An object of the present invention is to provide a cooler box that can be operated from a low-capacity, inexpensive power supply easily available to the user but that nevertheless offers cooling performance comparable with that of a freezer. Another object of the present invention is to provide a cooler box of which the cooling performance is variable according to what is to be cooled in it. Another object of the present invention is to provide a cooler box with more uniform interior temperature.
An object of the present invention is to provide a cooler box that can remove frost covering a cooling element so that stable cooling performance is obtained continuously from a cooling device.
An object of the present invention is to provide an energy-saving cooler box that can cool food, drink, and the like placed inside it or keep them cool while maintaining their freshness by storing cold produced by a cooling device.
To achieve the above objects, according to the present invention, a cooler box including a box member that has a hermetically closable cooling chamber formed therein and that insulates heat and a cooling device that cools the interior of the cooling chamber is characterized in that the cooling device is a Stirling-cycle refrigerator. With this construction, since the cooling device is a Stirling-cycle refrigerator, it is possible to realize a cooler box that can be operated from an easily available low-capacity, inexpensive power supply and that can cool a to-be-cooled article to a low temperature comparable with that produced by a freezer.
Here, the box member may be composed of a body member that has the cooling chamber formed therein and a lid member that is detachably fitted to the body member so as to open and close the cooling chamber, with the cooling device fitted to the lid member. This makes it possible to detach the lid member and wash it in its entirety, ensuring easy cleaning.
The box member may be composed of a floor wall and side walls that extend upward from the edges of the floor wall, with the cooling device fitted to the floor wall. This helps reduce the thickness of the side walls and thus the floor area occupied by the cooler box.
The cooling device may be fitted to the box member with its low-temperature head located below the high-temperature head. This prevents the air heated by the high-temperature head from making contact with the low-temperature head, and thus helps minimize the loss of cooling efficiency.
As the cooling device, a plurality of cooling devices may be provided that can be driven independently of one another. This makes it possible to cope with various set temperatures and various cooling patterns, and to obtain more uniform temperature.
The box member may have one or two pair of opposite side walls, with the cooling device fitted to each of the opposite side walls constituting each pair. This makes it possible to obtain more uniform temperature.
The cooling device may be detachable. This makes it possible to attach a cooling device most suitable to cool a given article and thereby achieve efficient cooling.
There may be additionally provided a liquid nitrogen container for instantaneously freezing a to-be-cooled article placed inside the cooling chamber. This makes it possible to cope with an article that needs to be cooled or frozen instantaneously.
The volume of the cooling chamber may be variable. This makes it possible to adjust the volume of the cooling chamber according to a to-be-cooled article so as to achieve efficient cooling.
There may be additionally provided a cooling element disposed at the low-temperature head of the cooling device and air circulating means for circulating the air inside the cooling chamber so as to bring the air into contact with the cooling element. This makes it possible to cool the air inside the cooling chamber by the cooling element and circulate the cooled air inside the cooling chamber so as to obtain more uniform temperature.
The cooling element may have a heat pipe. This makes it possible to conduct the low temperature produced by the Stirling-cycle refrigerator efficiently to the cooling element, and thus to cool the air inside the cooling chamber efficiently.
The Stirling-cycle refrigerator may be of a free-piston type that has a displacer reciprocating inside a cylinder filled with a working gas. This contributes to miniaturization and weight reduction.
According to another aspect of the present invention, a cooler box that includes a heat insulating box member having the interior thereof divided into a machine chamber and a cooling chamber and that cools food or drink placed inside the cooling chamber by introducing cold, produced by driving a Stirling-cycle refrigerator disposed inside the machine chamber, into the cooling chamber through a cooling element is characterized by the provision of frost removing means for removing frost covering the cooling element.
Here, the frost removing means may be heat generating means provided separately from the Stirling-cycle refrigerator. This makes it possible to energize the heating means as required to defrost the cooling element quickly.
The frost removing means may be waste heat conducting means for conducting the heat rejected from the heat rejecting portion of the Stirling-cycle refrigerator to the cooling element. This makes it possible to defrost the cooling element by exploiting the waste heat rejected from the heat rejecting portion.
The waste heat conducting means may be composed of: a first conduit for circulating a fluid between the heat rejecting portion of the Stirling-cycle refrigerator and a heat exchanger disposed away from the heat rejecting portion; a second conduit for circulating the fluid between the heat absorbing portion of the Stirling-cycle refrigerator and the cooling element disposed away from the heat absorbing portion; and flow path switching means located at where the first and second conduits cross each other to permit the first and second conduits to communicate with each other so as to form a single closed circuit.
The machine chamber may have the interior thereof divided by a partition wall into a cooling side where the cooling element is disposed and a heat rejecting side where the heat rejecting portion of the Stirling-cycle refrigerator is disposed, with the frost removing means composed of: a first valve for opening and closing an opening through which the cooling side of the machine chamber and the cooling chamber communicate with each other; and a second valve for opening and closing one of an opening formed in part of the partition wall or an opening formed between the heat rejecting side of the machine chamber and an exterior space. In this construction, when the first valve is closed and the second valve is so turned as to open the opening formed in the partition wall, the heat in the heat rejecting side of the machine chamber is conducted to the cooling side, achieving the defrosting of the cooling element.
The frost removing means may be phase difference controlling means for raising the temperature of the heating element by operating, with completely or substantially no phase difference, a piston and a displacer disposed inside a cylinder of the Stirling-cycle refrigerator so as to reciprocate along the axis of the cylinder. When so operated, the Stirling-cycle refrigerator does not constitute the normal reverse Stirling cycle, but only generates heat in the expansion space. This heat is conducted through the heat absorbing portion to the cooling element so as to remove the frost covering the cooling element.
The Stirling-cycle refrigerator may be of a free-piston type that has a displacer reciprocating inside a cylinder filled with a working gas. This contributes to miniaturization and weight reduction.
According to another aspect of the present invention, a cooler box that includes a heat insulating box member having the interior thereof divided into a machine chamber and a cooling chamber and that cools food or drink placed inside the cooling chamber by introducing cold, produced by driving a Stirling-cycle refrigerator disposed inside the machine chamber, into the cooling chamber is characterized by the provision of cold storing means for storing the cold disposed inside the cooling chamber. This permits part of the cold introduced into the cooling chamber to be stored in the cold storing means disposed in the cooling chamber.
Here, the cold storing means may be a sheet-shaped cold storing member laid along part or all of the bottom and side surfaces of the cooling chamber.
The cold storing member may be laid also on the undersurface of a door that opens and closes an opening formed in the top face of the heat insulating box member.
The cold storing means may be a granular cold storing material disposed near the opening through which the cold is introduced into the cooling chamber.
The cold storing member may be made of a metal having high thermal conductivity.
The cold storing member may be composed of a material having a cold storing capability sandwiched between plates of a metal having high thermal conductivity. This helps enhance the cooling performance per unit area of the cold storing member.
The cold storing member may be detachable. This makes it possible to detach the cold storing member as required when the cooling chamber is cleaned.
The cold storing means may be a cold circulation path formed along the side surfaces of the cooling chamber. This permits part of the cold introduced into the cooling chamber to circulate through the circulation path and thereby store the cold.
The Stirling-cycle refrigerator may be of a free-piston type that has a displacer reciprocating inside a cylinder filled with a working gas. This contributes to miniaturization and weight reduction.
According to another aspect of the present invention, a cooler box that includes a heat insulating box member having the interior thereof divided into a machine chamber and a cooling chamber and that cools food or drink placed inside the cooling chamber by introducing cold, produced by driving a Stirling-cycle refrigerator disposed inside the machine chamber, into the cooling chamber is characterized by the provision of cold storing means for storing the cold disposed inside the machine chamber. This permits part of the cold obtained by driving the Stirling-cycle refrigerator to be stored in the cold storing means disposed in the machine chamber.
Here, the cold storing means may be a cylindrical cold storing member disposed inside the low-temperature portion, including the expansion space, of the Stirling-cycle refrigerator.
The cold storing means may be a sheet-shaped cold storing member laid so as to enclose the Stirling-cycle refrigerator.
The cold storing member may be made of a metal having high thermal conductivity.
There may be additionally provided a cooling fan for agitating the air inside the cooling chamber. This helps obtain uniform temperature distribution inside the cooling chamber.
There may be additionally provided an indicating means for indicating that the cold is being stored by the cold storing means. This permits the user to easily recognize whether the cold is being stored or not.
There may be additionally provided a switching means for choosing whether to use the cold storing means or not. This permits the user to freely turn on and off the cold storage mode.
The temperature at which to keep the interior of the cooling chamber may be adjustable according to use. This permits the user to freely change the temperature at which to keep an article place inside the cooling chamber according to the type or the like of the article.
The Stirling-cycle refrigerator may be of a free-piston type that has a displacer reciprocating inside a cylinder filled with a working gas. This contributes to miniaturization and weight reduction.